A fast passive integrator

This article describes a passive integrator designed to exploit the risetime capabilities of the 7A29 preamp in the Tektronix 7104 oscilloscope. The present application for this device is to integrate the signals from current and voltage probes on the NRL electron autoaccelerator. This device addresses three problems encountered with simple RC integrators. First, the parasitic capacitance across the resistor causes the output to overshoot when given a fast rising input. Second, the integrating capacitor will display a self resonance because of its inductance. Third, a preamp with a high input impedance is needed to avoid shortening the integrator decay time. This problem is solved by compensating the parasitic capacitances, keeping the resonances fast and damping them, and resistively coupling to the preamp.